Flashing Glow Plug

[ejallison1]

I had a flashing glow light about a year ago on my B4 sedan which resolved after installing a new brake light switch. The glow plug started flashing again a month ago . Looking for suggestions on what to do or where to look for a solution. Here is what I've done so far. Haven't noticed any issues with the car's preformance. It is stock.

I again changed out the brake light switch and this time changed out the blue switch (assoc. with the cruise control) that is located immediately above it. Very difficult access!

I also changed out the switch on the clutch pedal.

All switches were new and checked with a a multimeter prior to installation and everything is working as it should. Cruise control works and cuts out when brake or clutch pedal is depressed. Brake lights working and are regular incandescent type.

I have VAG Com and went to group 6 which shows the switch functions. 011 is displayed initially and when the brake is depressed the numbers change to 000. When the clutch pedal is depressed the first of the three digits changes to 1. I do not have any trailer light wiring.

Vag Com shows the following on autoscan.:

Address 01: Engine Labels: 028-906-021-AHU.lbl
Part No: 028 906 021 FA
Component: 1,9l R4 EDC G10SG 1453
Coding: 00002
Shop #: WSC 25121
VCID: 53AB808CA184FD1EFE-4B00

3 Faults Found:
01268 - Quantity Adjuster (N146)
35-10 - - - Intermittent
00741 - Brake Pedal Monitoring
27-10 - Implausible Signal - Intermittent
01050 - Glow Plug Monitoring
35-00 - -
Readiness: N/A

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 6N0-909-60x-VW2.lbl
Part No: 6N0 909 603 G
Component: AIRBAG VW2 V00
Coding: 00071
Shop #: WSC 00046
VCID: 366DD9181236C836F9-4B64

2 Faults Found:
00532 - Supply Voltage B+
06-10 - Signal too High - Intermittent
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent

Checked the QA on VCDS and it showed 4.4-4.6mg/str which is where I had it set after the last timing belt change

Checked timing and it is 1/2 way between the upper and middle line on the graph.

I visually inspected the wiring on the 3rd injector as I had read it could be the cause for a flashing glow plug light. It looks OK.

Checked the glow plug harness and the glow plugs. Two glow plugs replaced and the harness appears good-no cracked insulation etc. and the autoscan above was done after I changed the two glow plugs. Can't remember if I cleared the codes.

Thanks in advance.

 

[Matt-98AHU]

The quantity adjuster code likely has nothing to do with the active reading for quantity while the engine is running. When you first "key on" the car, prior to the engine starting, the quantity adjuster does a quick self-check, moving from its minimum position to its maximum. If the voltage readings aren't within specs during that "sweep" at either stop position, it sets a quantity adjuster error.

You can view the results of this 'sweep' of min to max positions and what the voltage readings were at both extremes and get an idea of where the issue is. Sometimes the only solution is to replace the quantity adjuster or the entire pump, whatever is easier/cheaper for your budget and skillset.

Quantity adjuster codes ABSOLUTELY will cause a flashing glow plug light. As will the brake switch implausible signal code.

With that being said, let's take a look at the brake switch operation. You have two brake switches, and the primary reason for that is for the computer to be able to monitor the plausibility of the main brake light switch, ensure it's working correctly.

So, how this works is the brake LIGHT switch itself is open circuit when the pedal is untouched, it changes to closed circuit when pressed to send power to the taillights. The ECU also monitors the voltage here.

The second switch that is checking plausibility is the exact opposite. It is closed circuit, sending voltage to the ECU, when the pedal is not pressed, and changes to "open" when the pedal is pressed.

If you go to measured values, block 006, you should see in field 2 a set of zeroes. Should be 3 zeroes. The label file should have it labeled as "pedal monitoring"

The first 0 is actually for the clutch switch, the second two are your two brake switches. When you press the brake pedal, those last two zeroes should change from reading 0 to 1 simultaneously. If there is too much of a difference in time from when one is activate over the other, it will set that brake switch implausible signal code along with the flashing glow plug light.

Also, if there is inadequate current being drawn on the circuit, like, say, from installing LED brake light bulbs or from both bulbs being burned out, this often makes the computer set a code.

And there are patterns you can pick out with the values in block 006 if this is the case.

So, in block 006, second field, you'll see the 3 zeroes with the pedals not touched:

0 0 0

When you press the brake pedal it should look like this:

0 1 1

And those last two should change to 1 simultaneously. If they don't, it might just be a case of needing to adjust your brake switches.

Or, if they DO change to 1 at the same time, but the code still sets and when you release the brake pedal you see this:

0 0 1

This is usually what it looks like when it detects inadequate current being drawn on the brake switch circuit, when the last 1 stays a 1 after releasing the pedal.

Also, that lets you know which bit is for which switch.

Middle bit is for the plausibility switch.

Right bit is for the actual brake light switch.

 

[ejallison1]

Matt Thank you for taking the time to explain this. I will use VAG COM again and check group 6 to make sure the two digits are changing simultaneously when depressing the brake-hopefully an adjustment of the switches is all that is needed. Will research how to monitor the QA when "key on" prior to start with VAG COM. The glow plug light never flashes until after the engine has been started for 15-20 seconds. Can I assume that this would eliminate the voltage problem in the QA since the ECU checks the voltage prior to start up.